Help! How to get hold of gas fittings?

[loco]

I've just come back from my local gas supplier, who says that they can supply me with a regulator, tubing and tap, but won't supply me with any fittings unless I'm a registered gas supplier chap and the device is CE marked. Not good.

What do you guys use to get gas from the tank to the inside of the engine, and what sort of fuel rail do you use? I was going to go for a Simpson-style rail with holes drilled into it. The rail was going to have a thread on it, onto which a 'gas ftting' or sorts was going to connect to it, then from this a Cu pipe would lead onto a regular flexible hose.

I'm from the UK, so obviously laws are going to be different to Us/Euro laws... Any help would be greatly appreciated. I'm hoping to have the engine built tonight, so all that I'll need is fuelling, which of course I'm now stumped at.

Thanks again in advance.

[larry cottrill]

loco -

I don't remember if you are basically interested in "small" engines, as I am - but if that's the case, there is a simple solution. Use 1/4-inch brass "compression fittings" and pre-built "icemaker" hose. You can get away with this because you're using a regulator, i.e. you're delivering your gas at low pressure to your fuel nozzle. Here's how you set it up:

The OUTPUT (low-pressure outlet) of your regulator will probably have a 1/4-inch pipe thread hole (possibly with some fitting already installed - remove it with a wrench). Into this hole, thread a 1/4-inch NPT -to- 1/4 inch male compression fitting, with TFE tape or compound to seal.

Now, here's the trick: Compression fittings are designed for metal tubing - normally, you would cut off some 1/4-inch OD copper tubing, slip on the hex bonnet nut, slip on a compression ring, plug the tubing into the male fitting and use the bonnet nut to pull the coupling together, compressing the ring around the tubing. You're probably familiar with this. BUT, you can get pre-rigged refrigerator "ice-maker" lines with special ends that mate with the male compression fittings but use a rubber (neoprene, really) O-ring to form a seal under the bonnet nut. These hoses are available in at least two lengths - I can get one ten ft long if needed. because you're using the regulator, the hose is more than adequate (it will take at least 60 PSI water pressure in its intended use), and the O-rings mean it will seal perfectly on the male fitting when tightened by hand without even using a wrench (though you can if you want to). The outside of the hose I get is braided nylon or some such - very rugged and strong, but still flexible. People who see it think it's stainless!

On the other end (your engine fuel pipe), make sure you provide a long enough tubing section to keep the hose well away from the hot surfaces of your engine. Using 1/4-inch tubing, you rig the end with a 1/4-inch -to- 1/4-inch compression COUPLING (two identical male ends). On the tubing side, you naturally use the supplied bonnet nut and compression ring, as described already. Once that's tightened down hard (two wrenches in opposition), it becomes a solid end you can attach the other end of the hose to, as above.

It's about the simplest thing in the world. Of course, you could go bigger with 3/8-inch compression fittings, but then it becomes harder to find long hoses pre-built with the larger 3/8-inch ends. I get all the materials described here at big DIY retailers like Menards, Lowe's and the like.

Of course, the hookup described here is not "certified" in any way, so you're on your own if the Propane Police come for a visit ;-) But it is excruciatingly simple, and really works. The only difference between my description and the attached photo is that I used a small needle valve at the regulator outlet instead of a simple fitting, since I prefer to control flow and hold a constant pressure - the outlet of the needle valve is, indeed, a standard 1/4-inch compression thread.

L Cottrill

[loco]

Many thanks for the detailed reply!

I'm building a fairly large engine, in the order of 86lbs of thrust on paper. I guess I'll be using a whole lot more gas than the smaller models...
I'll take a look for the parts, although I think a lot has gone metric here, so I'll be looking for the metric equivalents of the parts you described.

I'm going to take a look around my local hardware suppliers and do some more research. At a first glimpse, there doesn't seem to be too many online suppliers.

thanks again.

[lucky rookie]

tell me what you need loco i can send by post if you want

[loco]

tell me what you need loco i can send by post if you want

Thanks so much! the probelm is, I'm not 100% sure what it is I
I'm looking for. As I said, I intend on making a fuel rail from a pipe with several holes drilled in it. I need a fitting to attach to it that will take a copper pipe to go back to the flexible tube from the regulator. I've attached a couple of photos from the guide to demonstrate. Apparantly I'm looking for a standard pipe fitting, but i'm not sure which standard, size, etc.

it's a big pulsejet, so will need a lot of fuel....

[JetSet]

I'm not sure of all the techy words, i generally just go into shops and say "i need one of these" or think "that looks roughly what I want, does it fit, yes, buy it"

Having made a large-ish lockwood in the UK I can help you a tiny bit. With regards to the propane tank end of your setup, you probably wont get enough fuel through the standard regulators we have over here, and getting hold of a reverse threaded propane tank nut (1 1/4" if i recall correctly, but its been a while) is a pain, I have been there too.

By far the easiest thing to do is go to a shop that sells propane cylinder coupling devices, or regulator extension hoses. Look around the gas fittings sections of camping and welding shops. The fitting you are after will be on 1 end of a tube, I think they call them pigtails. About 7 quid. Cut off the crimp carefully, pull of the tube and you will find the fitting you are after - minus the regulator :-) You might be lucky and find the other end of the pigtail has the fitting you are after, or be able to find a way of adapting it to your requirements.

[loco]

I'm not sure of all the techy words, i generally just go into shops and say "i need one of these" or think "that looks roughly what I want, does it fit, yes, buy it"

Having made a large-ish lockwood in the UK I can help you a tiny bit. With regards to the propane tank end of your setup, you probably wont get enough fuel through the standard regulators we have over here, and getting hold of a reverse threaded propane tank nut (1 1/4" if i recall correctly, but its been a while) is a pain, I have been there too.

By far the easiest thing to do is go to a shop that sells propane cylinder coupling devices, or regulator extension hoses. Look around the gas fittings sections of camping and welding shops. The fitting you are after will be on 1 end of a tube, I think they call them pigtails. About 7 quid. Cut off the crimp carefully, pull of the tube and you will find the fitting you are after - minus the regulator :-) You might be lucky and find the other end of the pigtail has the fitting you are after, or be able to find a way of adapting it to your requirements.

Cheers for the help!

What exactly does the reverse threaded propane tank nut do? are there high-flow regultors out there? What sort of flow rates and pressures should I be looking for from this regulator?

The problem is, I live on jersey where there is only one gas supplier. The gas supplies place is one of those setups where you go to a counter and ask the guy behind it. He goes off and brings you back what you need. Of course, for this you need to know exactly what you want, and there's practically a dress code of overalls. I turned up today in my work suit with a crap diagram of a fuel rail and the bits I need. The chap just pointed me over to the gas inspector behind me and he in turn said no... d'oh!

I'm going to do some research online, but it's looking tricky. Perhaps If I can't get sufficient propane flow, I'll go for what I orginally planned which was to start the engine with propane, then once hot, flip over to JET-A1 fuel.

Curse this age of health and safety!

[JetSet]

If you have a regulator already, take it off the tank and chances are, it will look like the image I have attached.

The screwey bit on the left (i didnt mean nut, i know what i meant hehe) threads into the tank valve. The nozzle bit on the right is what you connect the hose to. The big round flow-restricting regulator of doom is the bit in the middle. I personally dont think a regulator will allow enough fuel to come out of the tank for an engine of your size, so you will need to get rid of that bit, so its just the left bit and the right bit together

The second image I have uploaded is a propane pigtail, which has the fitting that goes straight into the bottle valve, and a piece of hose, which will let you leave the regulator out. If you cut off the other connector (or find fittings for that to connect to your pj) then it will be standard 8mm hose, allowing you to thread a bit of pipe down it with a jubilee clip, saves messing around with gas stuff. I found the pigtail here (I assume you are using calor or equiv.); http://www.caravanning-online.co.uk/aca ... hoses.html

[loco]

Thanks so much for the help,. I'm really begining to get a clear picture of what's needed! I didn't realise skipping a regulator was a possibility...

Are threads for all gas fittings reversed? I ask as I'm looking to install a ball valve and maybe a flash supressor for some safety with this somewhat dodgy set-up. If not, I'm guessing I'm looking for an adapter that goes into the tank on one end and has a regular thread the other side. After that, I can mount the tap/valve and supressor, then another adapter to fit the pipe/line to?

Sorry for the 100 questions, but there isn't really anywhere local that allows me to just browse about the various gas fittings. I really should befriend the gas man!

As an aside, take a look at the progress I've made with my first ever pulsejet... hoping to get it welded together over the next few days as the weather improves...

[larry cottrill]

Are threads for all gas fittings reversed?

No, the connection to the tank is left-hand - from that point on, everything can be normal pipe fittings or compression fittings. Welding outfits are an exception - all the gas fittings are left-hand threads, right out to the torch; all oxy fittings are right-hand. Prevents a lot of accidental disasters when fuel and oxygen are used together. Strangely, the little propane torch cylinders have a right-hand thread to screw the torch onto it - dumb. Fuel gas cylinders should ALWAYS have a left-hand thread, in my opinion. Make sure you ALWAYS use approved pipe compound or TFE tape on pipe threaded fittings (tapered threaded ends) carrying flammable gases.

Take a look at an acetylene welding rig up close: Note that all the left-hand threaded fittings have a groove cut all around them, to indicate the LH thread. Another convention that should always be followed, but sometimes is not. The fuel hose is always red rubber; the oxy hose always green. It all works together to prevent deadly mistakes.

As an aside, take a look at the progress I've made with my first ever pulsejet... hoping to get it welded together over the next few days as the weather improves...

loco, that looks like it will be a nice one!

L Cottrill

[loco]

loco, that looks like it will be a nice one!

L Cottrill

Thanks! I'm hoping my welding skills are up to it!

OK, I've found a handy gas supplier online. do you guys think the following setup would work. First, the pigtail connection would screw directly into the tank (is it me, or does it look ike the thread isn't reversed?). On the other end, I'd prise away the connector, to leave the 6.3ID pipe. This would then fit snugly onto the 8mm nozzle of the ball valve. On the other end there's a 1/4" compression fitting, which I'd attach a copper pipe (if possible) or plastic which would then go to a copper pipe.

Do you think this would work?

Here's the website:
http://www.bes.ltd.uk/nav_graf/frames_cat.html
The pigtail is under LPG & Oil -> hose &pigtail assemblies -> pigtail assemblies
The valve is under LPG & Oil -> Ball, Needle & Shutoff valves

Thanks guys.

[larry cottrill]

loco -

Yes, I think that looks OK. The drawing is just ... wrong, in terms of the threads shown. Because this is a high-pressure hose, be sure you tighten the hose connection with a proper size hose clamp after forcing it on there. The bad part of a ball valve is that it is inherently non-linear: very touchy at the low-flow end, insensitive at the high-flow end. The GOOD part is that you can shut it off instantly in an emergency, or after rich extinction flameout.

You will find a little ring supplied under that bonnet nut, which will tighten hard onto your 1/4-inch copper tube (unlike pipe, tubing is always "called" by its outside diameter). It will give you a good, gas-tight seal once it's together and tightened down (you push the tubing through the nut and ring, all the way into the fitting, then tighten). Once you put it all together and open the tank valve, you can brush a little detergent water on the fittings to check for leaks. Note also that you should NOT use any pipe compound on the pigtail fitting or the compression fitting - that's only for threaded pipe!

You will find that the pigtail threads easily into the tank valve, then "tightens up" rather suddenly. That's a "dome and cone" type fitting - the dome shaped nose of the hose fitting presses against a hollow cone shaped seat in the tank valve. Extremely good seal, BUT you MUST keep the mating surfaces free from sand, dirt, etc. to keep it that way! If you ever drop the pigtail on the floor, wipe the domed barb end clean and inspect it carefully to make sure it's not scratched or dented where it has to seal (you will see a slight "worn ring" around the critical zone, eventually).

L Cottrill

[Jason]

Sorry to bother you sir but with the regulator on LPG cylinder, i cant get enough fuel in my engine cause i want my engine to move forward and for this i need a lot of pressure and fuel flow.

The problem is this that many people told me that without the regulator on, i will get the LPG container blow up as there will be a flashback from the engine......Please i need a little HELP!!!

[loco]

Hi all, me again.

Well, bought the gas fittings as above, but I think I'm going to have to start over.

The good news is that on the engine side, I have the brass fittings and coper pipe that I require:

and even have a die so I can screw the fittings onto an 8mm tube, like so:


I bought the pigtail, and modified it to fit on the tap, but unfortunately, the other end is 6mm, plus the flow arrow on the tap points the other way, and finally it says it can take a maximum of 20Bar, whereas the output of an LPG tank is around 35bar.



So, now I'm looking for a pigtail connector that connects to a ball valve, which in turn has an 8mm compression connector. The chap at my local gas supplier really seems to have taken a dislike to me for some reason (note for all: don't tell them you're making a jet engine), and refuses to sell me parts, despite there being a legal waiver clearly stated at the desk, and my being totally prepared to sign whatever I need to in order to be able to take responsibility for my own actions.

Does anyone know where I can get these simple parts? I can't find any online which is most frustrating.
thank-you all very much, yet again. The engine is getting there slowly but surely!!

[Jason]

Sorry to bother you sir but with the regulator on LPG cylinder, i cant get enough fuel in my engine cause i want my engine to move forward and for this i need a lot of pressure and fuel flow.

The problem is this that many people told me that without the regulator on, i will get the LPG container blow up as there will be a flashback from the engine......Please i need a little HELP!!!